It is well established that abrupt cessation of sex hormone production in men and women causes bone loss. Several studies have demonstrated that androgen deprivation therapy (ADT) in men with prostate cancer increases the risk of osteoporosis and fractures. As the age at diagnosis of prostate cancer decreases, the use of ADT increases, and life expectancy improves, more men will be living a substantial portion of their lives with sex hormone deficiency and a higher risk of osteoporotic fracture. We propose a planning grant for a future clinical trial that will compare the efficacy of intervention with bisphosphonate therapy (with calcium and vitamin D), versus calcium and vitamin D alone, in men with prostate cancer who are being treated with ADT. Specifically, we plan to study African-American men, who have been underrepresented in other such trials. We plan a 2-year, randomized, double-blind trial of once-weekly oral bisphosphonate therapy plus daily calcium and vitamin D supplementation, compared with once-weekly placebo and daily calcium and vitamin D supplementation. Either alendronate or risedronate will be used for the bisphosphonate arm, to be determined during the planning phase. Bone density, biochemical markers of bone turnover, and body composition will be measured at regular intervals. Measures of free testosterone and gonadotropins will be obtained as part of routine clinical care. Fractures will be noted. The specific aims for the proposed planning grant include identification of additional clinical sites and clinical coinvestigators; refinement of the study design, including choice of bisphosphonate, sample size, and randomization scheme; development of a strategy to maximize recruitment and retention; preparation of a manual of procedures; and organization of a data safety monitoring committee. We believe that this planning period will allow us to develop specific elements essential to the success of the proposed trial without adding a lengthy organizational period to the actual trial. We also want to ensure that culturally sensitive, effective recruitment tools are in place.